Ionic Liquid-Based Electrolytes for Secondary Mg batteries

(Invited Presentation) The development of innovative electrolytes is one of the most crucial targets in order to devise secondary batteries running on alkaline- and alkaline-earth elements characterized by a high specific energy and power and an extensive cyclability, able to provide power for a wide range of applications ranging from portable electronic devices to light-duty electric vehicles. The electrolytes must satisfy very demanding requirements, including: (a) easy migration of the alkaline- and alkaline-earth cations between the electrodes of the battery; (b) high compatibility with all the other functional materials used in the assembly of the device; (c) wide potential window and excellent stability.1 This report summarizes the preparation and characterization of innovative families of ionic-liquid (IL) -based electrolytes meant to address these issues, thus opening new and promising avenues for the research in this field. The electrolytes are based on δ-MgX2 magnesium salts, AlX3 and 1-Ethyl-3-methylimidazoliumX ILs (with X=Cl-, I- or BF4-). 2,3,4 The resulting electrolytes are suitable for application in secondary Mg batteries, and demonstrates: (1) a conductivity at room temperature higher than 10-3 S/cm; and (2) good electrochemical performance. The chemical composition of the electrolytes is analyzed by ICP-AES and microanalysis. The thermal properties are investigated by HR-TG and DSC measurements. The structure and the interactions in materials is studied by vibrational spectroscopies (FT-MIR and –FIR). The electric response is elucidated by Broadband Electrical Spectroscopy (BES). Results allow to propose a conduction mechanism and to define the interplay existing between structural, thermal transitions and electric properties of proposed innovative electrolytes. (1) Di Noto, V.; Lavina, S.; Giffin, G. A.; Negro, E.; Scrosati, B. Electrochim. Acta 2011, 57, 4–13. (2) Bertasi, F.; Hettige, C.; Sepehr, F.; Bogle, X.; Pagot, G.; Vezzù, K.; Negro, E.; Paddison, S. J.; Greenbaum, S. G.; Vittadello, M.; Di Noto, V. ChemSusChem 2015, 8, 3069–3076. (3) Bertasi, F.; Sepher, F.; Pagot, G.; Paddison, S. J.; Noto, V. Di. Adv. Funct. Mater. 2016, DOI: 10.1002/adfm.201601448. (4) Bertasi, F.; Hettige, C.; Greenbaum, S. G.; Vittadello, M.; Di Noto, V. Ionic Liquid Comprising Alkaline Earth Metal. PCT Patent App. No. WO2015/069871, 2014.